Trends in the Use of Copper Wire & Cable in the USA

By William T. Black
Vice President – Electrical & Electronic Markets
Copper Development Association Inc.

A version of this paper was presented at Copper 95 in Santiago, Chile in November 1995


This paper summarizes the 25-year trends, from 1970 to the present, in the most important copper wire and cable markets in the USA. The assumption is made that, while wiring practices may vary widely from country to country, including use of conductor materials as well as usage intensity of each type of wire and cable, nevertheless historical US trends, and their implications for the future, should be instructive for much of the rest of the world. Overall, shipments of copper electrical wire and cable products were 1,541,000 tonnes in 1994, and have grown at an average rate since 1970 of 1.4%/year. Copper’s largest market, building wire, is also one of its fastest growing, and there is reason to believe that this growth should continue indefinitely.

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This conference is oriented mainly to extractive metallurgy matters: the extraction and concentration of ore, the conversion to copper metal and the refining of copper to final purity suitable for commerce, mostly cathodes of high purity. In the USA, to cite one interesting statistic, more earth is moved in the extraction of copper than for all other metals combined – even including iron, of which 40 tonnes are used for each tonne of copper consumed. Why is this? Because ore grades are so lean, and so much overburden must be moved to get at the copper. Yet despite this inherent disadvantage compared to iron, aluminum and other materials with which copper competes, the extraction process is so efficient that copper is well able to hold its own in the economic marketplace.

Those of us active in the promotion of new uses for copper, and the defense of existing ones, need to have an appreciation of where the metal comes from, and with what difficulty. Similarly, everyone involved in the production of copper should be aware of its important end uses and the trends, sometimes widely divergent, in each.

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Copper Wire & Cable Products

Wire and cable products are by far the major users of copper in the United States and, indeed, worldwide. In fact, in the USA more than 60% of all copper and copper alloys consumed are used because of electrical conductivity, and about 80% of that is wire and cable. Nearly all newly mined copper, the main interest of this conference, goes into the production of wire rod, and thence to wire and cable products. (Most of the copper consumed by the brass mill and foundry industries is recycled copper-base scrap, some fraction of which is re-smelted or re-refined before charging into the brass mill or foundry furnace.)

To draw conclusions allowing one to accurately predict the future for wire and cable, each wire and cable product – building wire, magnet wire, telecommunications cable, power cable, automotive wire and others – must be studied by itself as each has its unique characteristics, and the individual product trends are in many cases counter to each other. We will therefore develop the overall picture for copper wire and cable by analyzing the major products individually in order to better understand the future outlook for copper’s most important market.

In 1994, the latest year for which data are available (albeit preliminary), 1,541,000 tonnes (metric tons) of copper wire and cable were shipped, all but 85,000 of which was insulated. The trend has been generally upward and 1994 was in fact a record year. Over the last 25 years the average growth rate in copper use has been 1.4%/year.

Although the scope of this paper is limited to the USA, many of the trends it analyzes are in fact worldwide. The mix of copper shipments by cable type, however, is radically different from country to country, depending on local practices and traditions. In the USA electric utility power cable is installed predominantly overhead and is aluminum, while in other countries, for example the Netherlands, the tradition is to install power cable underground, and to use a significantly greater proportion of copper. The US standard for electrical service to homes is 120/240 volts (v), rather than a straight 240 v as in much of the rest of the world. This means that, for a given wattage of demand, the electric current in the US 120 v circuits is twice as large, resulting in the need for correspondingly larger wire on average, since conductor wire must be sized according to current. However, there are far more similarities than differences from country to country in wire and cable usage, and that is why this paper on US practices and trends is offered in an international forum.

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Building Wire & Cable

By far the largest consumer of copper in the USA is building wire, that wire used inside buildings of various types – residential, commercial or industrial. Over the last quarter century US building wire shipments have increased sharply. Shipments in 1994 (preliminary) were a record at 543,000 tonnes, somewhat ahead of the previous record year of 1987. For building wire a growth rate of 3.8%/year has been experienced over the period studied.

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Standard US Wire Gages

Building wire is largely a commodity product of standard materials and sizes. In the USA these sizes are expressed as American Wire Gage (AWG) and rated by the National Electrical Code according to their maximum safe ampacity – that is, their current-carrying capacity. The smallest size used for carrying currents up to 15 amperes (A) is AWG No. 14 (1.63 mm diameter). In general, even AWG gage numbers are standard building wire sizes, with the smaller AWG numbers corresponding to larger sizes. AWG 12 (2.05 mm) is the most common size, typically carrying 20 A and being used for branch circuits in non-residential as well as residential applications.

Wire size is important in analyzing the building wire market. A key factor in making building wire copper’s largest market, and one of its fastest growing, is a trend over recent years from AWG 14 to AWG 12 for the smallest size in building wiring. For an equal length of wire AWG 12 contains about 60% more copper than AWG 14.

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More larger wire is being used due to the ever-increasing demand for electrical services throughout buildings. This is a steady, undeviating trend regardless of whether the economy is in boom or recession – more appliances, both large and small, more computers, more television sets, VCRs and other electronic entertainment devices, more lighting – the list goes on and on. Only for space heating using electricity are there ups and downs, largely depending on the relative cost of electricity vs. natural gas and heating oil in a given geographic area.

Few basic materials are so fortunate as to have their major market also growing rapidly, and no serious competition from aluminum is in sight, nor is there reason to believe that the trend toward increasing use of electricity is likely to reverse in the near future. But copper’s healthy position in building wire serving traditional markets, which are themselves growing, is not the end of the story. There are still significant opportunities to improve copper’s position. Presently copper has 93% of the building wire market in the USA, compared to as little as 69% back in 1974. The rest is aluminum, mostly in two areas: feeder cable for commercial buildings and service entrance cable in residential structures. We have been studying the latter market and find some niches that copper could fill, particularly where the wire is pulled in conduit. Copper is recognized as the quality product, while aluminum is mainly used because it is cheaper. In feeder cable – larger sizes used in the commercial and industrial markets to feed subpanels, and perhaps carry large currents from floor to floor in a multi-story building – the aluminum industry has concentrated some marketing effort. It has been successful mainly in office buildings and shopping centers where cost pressures are greatest, and where quality materials are sometimes squeezed out in the bidding process. This cheapening of the final job is often masked by use of the term “value engineering”.

Copper’s unquestioned superiority over aluminum building wire is at the point of connection. Although improved aluminum building wire materials have been developed to alleviate the tendency for connections to loosen as the metal “cold-creeps,” no amount of alloying will change the inherent nature of aluminum to immediately form, upon exposure of a fresh surface to air, a tightly adherent, high-resistance oxide film. This means that aluminum building wire can only be properly connected if special techniques are used, such as the use of deoxidizing compounds. This requirement sharply narrows aluminum’s advantage of lower first cost for the material. If proper analyses were made, not only first cost, but life-cycle cost, must be considered. With aluminum extra costs over the life of the material may be associated with “callbacks” to tighten connections that have become loose, which in some cases might even lead to premature failures. A survey of US electrical contractors on their preference of building wire materials showed that they preferred copper 20 to 1 over aluminum. The only reasons for using aluminum were for lower first cost and light weight. Copper was considered superior in all other respects – connectibility, overall reliability, etc.

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Power Quality and Copper

There is a growing awareness in the USA, and presumably worldwide, of power-quality issues and the effect they have on the proper operation of modern electronic equipment. Most existing commercial buildings are inadequately wired. As the use of computers has proliferated, and particularly personal computers in the last decade, many problems have surfaced which can be traced back to inadequate wiring.

The most obvious problems are easily recognized: too few circuits, too few outlets, especially where they are needed, nuisance tripping of circuit breakers or fuses resulting from overloading. Solving or avoiding problems like these, both in commercial and other applications, is the main reason for the spectacular growth in building wire shipments.

But many other problems remain. In three-phase power distribution systems the fourth wire, the neutral, is commonly the same size as the power legs, and sometimes it is even smaller. (In some circuits, such as motor feeds, it may be left out entirely.) The theory is that the sine-wave currents in the three phases, being 120 degrees apart, cancel each other out, so that the return current should be small or zero. But this is not correct in the case of most electronic devices, particularly computers, printers and other office equipment, and variable speed motor drives. Their switched-mode power supplies tend to chop up the sine wave, operating at much higher frequencies than 50 or 60 Hz. It is not uncommon to measure effective neutral currents from 1 to 2 times as large as the currents on the power legs, although it takes special test equipment to even detect these currents. When the neutral wire is undersized, serious overheating may result and this becomes a safety issue. In some cases the effect of the electronic equipment is to also require oversized power legs, for reasons too technical for this paper. The problem of overheating of undersized neutrals continues all the way back to the distribution transformer serving the electrical load. “K-rated” transformers, containing oversized neutrals as well as other design changes, have been developed to alleviate these overheating problems.

Grounding systems are designed to protect people and equipment, and normally carry no current. Historically, insufficient attention has been paid to grounding, and the wiring in most commercial buildings is inadequate to maintain all parts of the system at a common ground potential. Computers typically operate at 5 volts, so an accurate Point 0 is important when one computer talks to another.

Without going into all the ramifications of inadequate grounding, commercial and industrial buildings, particularly those containing more than an average concentration of computer equipment, need low-impedance grounding systems, and many – probably most – don’t have one. Adequate grounding can mean many things, including large amounts of large-gage copper wire, both inside the building to hook up different parts of the building steel, and outside to assure adequate contact with the earth. To cite one example, one large research university, as a matter of policy, surrounds its buildings with 500 kcmil horizontal copper wire, interconnected with three ground rods at each corner of the building.

Perhaps the most common form of inadequate grounding is the use of steel conduit as the equipment ground. As conduit joints corrode, the impedance of the ground path can rise dramatically. A simple solution is to use a separate copper ground wire inside the conduit.

Power quality improvement, combined with replacing aluminum in those areas where it is used, and a continuing emphasis on more circuits, adequately wired and protected, together assure that copper’s growth potential in building wire, its largest market, is far from exhausted.

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Magnet Wire

Magnet wire has traditionally been the staid, unspectacular performer among wire and cable categories. Between two-thirds and three-quarters of magnet wire shipments are used in the windings of motors, with the remainder used in transformers, coils and other products. The numbers are actually somewhat higher than shown in Figure 3 to the extent that products not classified as magnet wire for product purposes (mostly enameled) are used to perform the magnet wire function. This is mainly bare wire and strip used in transformers. These additional categories add about 30,000 tonnes/year to the numbers shown.

In the last few years, magnet wire shipments broke out of a low-growth historical pattern (averaging 1.4%/year growth over the full 25-year period). Records have been set in each of the last three years, with a particularly sharp upturn in 1994, to 294,000 tonnes.

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Electrical Energy Efficiency

One of the most important reasons for this increase in the use of copper magnet wire has been the recognition that attention to electrical energy efficiency considerations benefits everyone involved. Energy efficiency is a win/win/win/win situation. For the end user of the motor or transformer, electricity costs are lower. For the electric utility, the need to conserve energy is met so that new generating capacity – expensive capacity, fraught with environmental problems that the utility would sooner avoid - does not need to be built. For the motor or transformer manufacturer, a higher value product with a higher profit margin is sold. And finally, for the copper industry, more copper is used.

On average about 25% more copper is needed for a premium-efficiency motor compared to a standard unit. The increase for transformers varies more widely from type to type; we have examples of increases varying from 30% to 150%, with an overall average increase in copper use for all types of perhaps 50% in going from standard to premium efficiency. Most of the industrial motors of interest are already copper; for transformers, however, aluminum is the standard in the USA, and therefore the rewards for an energy-efficient, copper-wound transformer are greater for the copper industry.

The copper industry’s approach in the USA, through CDA, is purely an economic one, as follows: to promote those energy-efficient electrical applications where lower life-cycle costs will result for the end user. This necessitates a careful analysis of each application. If a motor will run only 3 or 4 hours per day, for instance, a premium-efficiency unit will probably not be economical. By concentrating on the applications that will truly pay for themselves, we build trust among the end user community.

Our market development approach has been mass communications aimed at five target audiences: the industrial sector, power utilities, educational institutions, commercial and industrial buildings that are owner-occupied (and therefore where the owner not only selects the electrical equipment in the building, but also pays the electricity bill) and finally government buildings. In all these cases the specifier of the equipment has a vested interest in saving energy, so our message that his investment in efficient equipment will have a short payback is generally well-received and appreciated.

In addition, the manufacturers of efficient equipment appreciate our involvement in helping pull their higher profit motors and transformers through the distribution channels. We need their expertise to keep our message properly focused, and so we have a true partnership with them. Partnership is in fact the most important characteristic of the program, known within the industry as the Electrical Energy Efficiency Initiative.

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Cast Copper Motor Rotors

Although it is not a magnet wire issue, motor manufacturers want to replace cast aluminum rotors in integral and some sub-fractional horsepower motors, up to perhaps 250 hp, with cast copper rotors. Such a development would allow them to make a motor of a given efficiency smaller, with attendant savings in core steels and other materials of construction. The metallurgical problems of casting copper rotors are daunting, however, since die-casting temperatures of 1100-1200 C would be required, and new die materials need to be developed. We at CDA are actively involved in this issue.

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Fluorescent Lamp Ballasts

Our strategy for energy efficiency is to promote the most cost-effective products on a life-cycle-cost basis, which are not always the most efficient products that can be achieved technically. In the case of fluorescent lamp ballasts, a move is underway by the US Department of Energy (DOE) to perhaps ban magnetic ballasts (which contain copper windings) in favor of somewhat more energy-efficient electronic units with much less copper. We have been able to show that, for the large number of commercial and institutional applications where the lights are on about 70 hours per week or less, the higher cost of the electronic units is not repaid through energy savings in a reasonable time. In the case of magnetic lamp ballasts, we are supporting a product which, while quite energy-efficient compared to years ago when inefficient aluminum-wound units were the standard, is not the most efficient possible. However, the message we send is still consistent with our basic principle of supporting only those applications providing the user with lowest life-cycle costs.

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Telecommunications Wire & Cable

The upward trends observed in building wire and magnet wire do not hold true for telecommunications wire and cable. After a strong upward trend through the 1970s, shipments of telecommunications cable peaked in 1979, then moved sharply downward over the next few years, finally plateauing through the period 1985-1992.

This early drop during the 1980-1985 period was due mainly to two technical developments: the use of smaller wire sizes, particularly the replacement of AWG 22 with AWG 24 and 26 and the use of multiplexing (or subscriber carrier, as it is commonly known). It was not due to fiber optics. At that time fiber was firmly establishing itself in the long-distance market and in interoffice trunking, but had made no penetration into the subscriber loop, where copper use is concentrated.

This was followed by a period of relative stability through 1992, as growth in the telecommunications system balanced continuing losses due to subscriber carrier, and as fiber optics began to penetrate into the feeder portion of the subscriber loop. One trend reversed itself, however. The use of AWG 26 wire decreased and the regional Bell operating companies (RBOCs) moved back toward AWG 24 as a standard. (Similar to the comparison between AWG 12 and 14 in building wire, AWG 24 contains 60% more copper per foot than AWG 26.)

In the last two years copper use has dropped again, particularly in 1994, where the latest shipments data, though estimated, are 137,000 tonnes. Over the full 25-year period shown in Figure 4, copper’s growth rate has been a negative, -3.3%/year. Early results for 1995, however, indicate that the low 1994 shipments were an aberration, due to a temporary hiatus in RBOC purchases, with recovery in 1995 expected at least to 1993 levels. Nevertheless, fiber is now strongly penetrating the feeder portion of the subscriber loop, and threatening to penetrate ever deeper toward the final customer.

The trends in telecommunications are so fast-paced and changeable that it is almost impossible to keep up. In 1994 a growing interest was expressed by the RBOCs to install hybrid fiber-coaxial cable systems (HFC) to replace their existing copper plant. One company, Pacific Bell, serving part of California, made a firm commitment to this investment, and others made announcements. HFC was the technology-du-jour. But in recent months several companies have backed away from this commitment, and are now talking about pushing fiber closer to the customer than before, with only a short leg - perhaps copper, perhaps not – as the final link.

There is also a growing interest in the USA, and particularly in other countries around the world, in asymmetrical digital subscriber line (ADSL). This is a new technology that uses the latest capabilities in electronics to continuously check the quality of a signal passing down a copper line and make the necessary adjustments to keep it “clean.” It also uses digital compression technology sufficient that as many as four “canned” television signals, or two “real-time” signals, can be passed simultaneously down the line: an ordinary copper wire pair now going into virtually every home.

Most telecommunications professionals in the USA view ADSL as an interim technology at best, permitting the provision of broadband telecommunications services while buying time until the hundreds of billions of dollars needed to rewire the nation are accumulated and put into new plant. To us in the US copper industry, such an interim solution might be thought of as also buying time until even more powerful copper-based systems are developed. If the power of these evolving systems keeps ahead of the need for broadband services, the massive investments in new outside telephone plant might be postponed indefinitely.

No matter what the future of ADSL and other copper-based technologies that might evolve over the next few years, copper’s use in the outside plant of the telephone system is expected to decrease as fiber continues to move closer to the customer, one step at a time.

The use of copper in inside telecommunications wiring has grown with the computer industry. Local area networks (LANs), used to hook computers together within a building or group of buildings, primarily use unshielded twisted pair copper. The ever-increasing capacity of this product has allowed it to outrun the increasing needs to move large volumes of data from computer to computer. Category 5 wiring has a capacity of 100 megabits per second over short distances, due to the special care taken in manufacture, such as the accuracy of the twist. Even higher capacity cable is being designed and tested. Coaxial cable has lost market share to twisted pair copper in this market, and fiber optic cable, which has far more capacity than copper, of course, is simply not needed for the horizontal runs that make up most of the linkages.

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Power Cable

The wire and cable category known as power cable is really made up of two parts: cable used by the power utilities and industrial-type cable. In the case of utility cable, aluminum dominates in the USA. Most lines are overhead and in this case the light weight of aluminum is a definite advantage. The largest tonnages of overhead cable are aluminum-conductor, steel-reinforced (ACSR) cable, which is uninsulated. Various insulated and/or jacketed constructions are also used. Copper is used overhead in a few specialized applications where corrosion resistance is important, such as seaside locations.

When the utility cable goes underground, copper’s other advantages, such as smaller size to deliver a given ampacity and superior connectibility and corrosion resistance, often overcome its weight disadvantage. Underground cable constructions are more complex than overhead, and many use a combination of copper and aluminum, along with lead or other materials for sheathing or shielding. If direct-buried with a concentric neutral, copper is often used in contact with the earth in combination with an aluminum central conductor.

Overall, however, copper has only a small fraction of the power utility cable business in the USA. The utilities have developed techniques to connect aluminum properly, and have trained their personnel accordingly. There is little opportunity for copper to penetrate the utility market, particularly overhead, compared to the other aluminum wire and cable applications already mentioned.

In the case of industrial cable, on the other hand, copper has a dominant position. In such applications as welding cable, mining cable, trailing cable for walking draglines, etc., the reliability of copper is recognized, and no compromises are made by using other materials that might be cheaper on a first-cost basis.

Over the last 25 years there has been a long-term stability in shipments of copper power cable in the USA. The growth rate over the 25-year period is only 0.4%/year, with estimated 1994 shipments of 143,000 tonnes.

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Automotive Wire & Cable

Automotive wire and cable has had the fastest growth rate over the 25-year period of any category studied, 6.5%/year, with estimated 1994 shipments at 117,000 tonnes. This growth is mainly due to the rapid increase in the electrical and electronic loads in passenger cars, as well as utility vehicles, vans and even pickup trucks.

As automotive complexity has increased, the length of wire in harnesses has doubled, redoubled and redoubled again. Most wire in wiring harnesses is in the 14-22 AWG range. As electronic functions have been added, smaller size wire, to carry signals from sensors to computers, for example, has proliferated, so the increase in weight of copper has not been proportional to the increase in length.

In recent years the bottom-line increase in copper content per car has been about 5% each year. Space constraints guarantee that this cannot continue indefinitely; however, the options of multiplexing and fiber optics are quite expensive. It is expected that more copper will continue to be used in future years, but the rate of increase will moderate.

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Other Wire & Cable Products

We have not discussed a few other wire and cable types: apparatus wire, cord sets, electronic wire and cable (this category includes LAN cable, mentioned under Telecommunications), control and signal wire and cable, and bare wire, among others. In total they are significant C amounting to 307,000 tonnes in 1994, 20% of all US wire and cable shipped. However, each of these products is controlled by a different marketplace, and so the trends in total are not instructive.

Of the categories itemized above, it should be noted that electronic wire and cable, largely as a result of the growth in inside wiring (LANs) using unshielded copper twisted pair, has had a 25-year growth rate of 5.2%/year. This growth rate would have been much higher except for the fact that aluminum wire with a thin copper plating C not solid copper – is most commonly used for the fast-growing market of the coaxial cable used in cable television.

A period of growth may be ahead for bare wire, assuming success in efforts to greatly improve the outside grounding (earthing) systems for commercial buildings in order to alleviate power-quality problems.

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About 60% of all copper and copper alloys consumed in the USA are used because of the electrical conductivity of the metal, and about 80% of that is wire and cable. The percentage of newly mined copper used to produce electrical wire and cable is even higher, since most brass mill and foundry products are produced from recycled copper-base materials. Therefore, there is a close tie between what happens at the mine and what happens in the marketplace for copper wire and cable.

In the 25-year period since 1970 shipments of copper electrical wire and cable products in the USA have grown an average of 1.4%/year. Building wire in that time has grown 3.8%/year and has established itself as copper’s Number 1 market by a widening margin. On the other hand, telecommunications wire and cable, the former top market, has declined by 3.3%/year, with further declines in the future. Automotive wire and cable has been the fastest growth market at 6.5%/year, and other products – magnet wire, power cable, bare wire, electronic wire and cable, apparatus wire, cord sets – have all shown positive growth.

Though building wire is the largest market, its growth period should continue well into the future. The electrification of the office and home continue unabated, and the ever-increasing use of electronic devices has brought about power-quality problems that can best be solved by the use of more copper building wire (and bare wire) in grounding systems as well as in power legs and neutrals.

The second-largest wire and cable market, magnet wire, should benefit in coming years by the increasing attention on electrical energy efficiency. This results in more copper being used in those motors and transformers that are already copper, and a gradual switch to copper from aluminum, particularly in transformers which are presently predominantly aluminum in the USA.

Overall, the growth record of the wire and cable industry in the USA should continue many years into the future.

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